Roving machines serve for producing a roving which is used as a model for spinning into a fibre yarn, for example on a ring-spinning machine, a drawer sliver being drafted in a drafting arrangement of the roving machine, and this fibre composite subsequently acquiring a twist before it is wound as fibre stubbing, with a protective twist, onto a feed bobbin.
The slubbing serving as a model for ring-spinning machines is therefore usually produced from a drawer sliver which is drafted on a drafting arrangement of the roving machine, mostly on a double-apron drafting arrangement, and subsequently acquires a slight twist, so that this slubbing can be wound, free of distortion, onto a bobbin. The imparted twist should only be such that the cohesion of the fibre composite is sufficiently firm for winding and unwinding again and for the transport of the bobbins, so that no wrong drafts occur. On the other hand, in terms of distortion on ring-spinning machines, this twist must be so low as to give rise, in the further treatment process, to no draft faults which may be reflected, for example, in what are known as pull-throughs, yarn defects, dimensional unevennesses, imperfections or thread breaks.
To produce the slubbing, the roving machine uses is what is known as a flyer. This roving machine is equipped with a drafting arrangement and with a spindle for winding the flyer slubbing onto a roving tube by means of a flyer in order to support the slubbing with respect to the centrifugal force caused by the spindle rotational speeds. For this purpose, the roving emerging from the drafting arrangement is wound onto the roving bobbin-via the flyer rotating about a roving tube. The roving acquires a protective twist as a result of the rotational movement before it is deposited on the roving tube. For this purpose, the roving is guided by a flyer arm of the flyer and deposited on the roving body via a press finger on the flyer, the press finger being pressed against the roving winding body. Imparting the twist in the roving and winding the latter onto a roving tube take place, here, in one process step. For reasons concerned with the process, the roving tubes are oriented vertically.
The flyer is, particularly because of the winding, a complicated and costly machine in the spinning process. In addition, the conventional delivery capacity of a flyer is 20 to 40 meters per minute. However, this low production cannot be increased with regard to the winding system using flyers, since a higher speed is limited by the centrifugal force which the flyers must withstand.
Meanwhile, however, other forms of imparting the twist in roving machines are also known, which have in common the fact that a protective twist is applied to the roving in a twist-imparting member following the drafting arrangement, and the roving having a protective twist is subsequently supplied to a winding device. That is to say, imparting the protective twist and winding the roving take place in separate process steps and, correspondingly, in separate, that is to say functionally separated devices. Correspondingly, in such roving machines, other winding devices can be used which are akin, for example, to the conventional bobbin-winding concept.
Thus, for example, WO-A-2005/026421 describes a method for producing a roving, in which imparting the twist takes place pneumatically in a nozzle block, in a similar way to the airjet spinning method. The roving experiences a genuine twist as a result of rotating air vortices.
WO-A-2004/042126 likewise describes a pneumatic imparting of twist, but, here imparting the twist takes place according to the two-nozzle principle. That is to say, the twist-imparting member contains a first twisting chamber, through which the sliver is conducted and acquires a twist by means of airjets. In a second twisting chamber of the twist-imparting member, the sliver acquires an opposite twist, likewise by means of airjets, so that a false twist is imparted to the sliver.
Furthermore, Swiss Patent Application CH 00044/08 describes a twist-generating member in the form of false-twist elements, for example rubbing rollers, in which the sliver is provided alternately with S- and Z-twists and is subsequently combined automatically into a roving self-twine. The roving self-twine is wound onto a roving tube in a winding device. The roving self-twine is opened into individual roving fibre strands again only in the ring-spinning machine.
What the three roving production methods according to the abovementioned patent applications have in common is that twist generation takes place independently of the winding of the roving in functional terms. This makes it possible to use a winding apparatus for the roving which is not possible in the case of conventional flyers.
An especially suitable winding apparatus is guided by the known bobbin-winding machine in which yarn is transferred at high speed from the top onto a yarn bobbin.
Such a device contains a bobbin mounting, in particular a creel or a bobbin mandrel, for the rotatable mounting of a roving bobbin and also a traversing device for traversing the roving to be wound, in relation to the bobbin, in the axial direction of the bobbin. The roving may be deposited in a parallel-wound or cross-wound package, substantially higher traversing speeds being adopted in the latter winding method.
In contrast to the yarn, the roving has a considerably lower strength because of its low twist which is of course merely a protective twist. If, then, the roving is to be wound at high speed onto a roving tube, without wrong drafts or even roving breaks or later yarn breaks occurring, the take-over of conventional winding devices is unsuitable. Particularly in the region of the traversing device, considerable problems arise when roving is being wound and may lead to wrong drafts or even roving breaks.